Defeat at Doncaster means Pompey have won just one of their past five League One fixtures.
But Jack Whatmough believes they still have the requisite character to remain in the promotion hunt.
The 2-1 reverse saw them drop to fifth in the standings, with just a two-point gap to Ipswich in seventh.
And Whatmough has urged for unity in the camp as the Blues look to turn their stuttering form around.
The defender said: “I’ve been around this first team for seven years and in terms of spirit, this is the best group I’ve been involved in.
“People just need to stick with us because it will turn around – this is definitely the best dressing room.
"It’s not going for us at the moment, but we’ve got the ability to turn it around. The character is here to do it."
“There’s a real togetherness and everyone is here for the same reason, which is to secure promotion.
“We all want it and won’t stop working towards that. It’s something we spoke about after the match.
“It’s not going for us at the moment, but we’ve got the ability to turn it around. The character is here to do it.”
Pompey will need to improve on a run of form that has seen them beaten in half of their past 10 fixtures.
Whatmough said: “The players are as frustrated as anyone. It’s not clicking at the moment, but it will.
“There are a lot of points for us still to play for and we’ve got a strong group all working towards the same thing.”